Why did Germany invade Russia?
At the end of 1940 Hitler was anxious to end the war. It had been a great strain on the nation and economy and seemed to be winding down. He was applying his mind to the post war period and was in negotiations with the Italian, French and Japanese to find a kind of equilibrium for the New Order. He also wanted an understanding with the Soviets. He invited the Russia Foreign Minister, Molotov, to Berlin to work out an understanding and told him that there didn't have to be a conflict of interest between Germany and the Soviet Union as long as each country respected the other's sphere of influence, which he mapped out. He stated that Soviet-German cooperation had been mutually beneficial and Molotov agreed. Hitler told Molotov that it would take Germany 100 years to fully utilize the new teritories she had acquired as a result of the war and that she would look to her old colonies in Africa for Lebensraum or new lands to colonize. :)
However, in the course of his discussions with Molotov, Hitler perceived the Soviets to be hostile, accusatory and making difficulties. There was an emnity there from the Soviet side that could not be overcome and Hitler began to suspect the Soviets might be planning an attack on Germany. He ordered the planning for Operation Barbarossa (the attack on the Soviet Union) as a contingency if the political process broke down.
Many believe that Hitler wanted to attack the Soviets simply to control more territory and to destroy Communism, perhaps. However I believe the strike was one of preemption. Certainly Germany didn't need any more new territories and the country was war-weary. Hitler himself, though he was an anti-communist, didn't really care all that much about the goings-on outside of Germany and what he considered the German sphere of influence. He heart was really for Germany and some of the territories of the old Austro-Hungarian Empire for which he had a sentimental attachment, having been born into that great and cosmopolitan empire. Certainly the campaigns in Norway, Greece and Africa were for preemption - to deny England areas of operation. The sad truth for Germany and the world is that the two alpha dogs of Europe, the Nazi Regime and the Soviet Union were destined to have it out. Despite the fact that the war with England was still unresolved, Hitler decided to strike first.
The Nazis were extremely hostile to Communism. Hitler's great ambition was the eradication of Communism. In fact, one of the main reasons for the establishment of the Nazi party and its immediate predecessor was the complete destruction of what the Nazis called 'Jewish Bolshevism'.
Boundless expansion in Eastern Europe (not in Africa) had been the key goal of German nationalism since 1917-18 or even 1914 ... To portray the war against the Soviet Union as the result of personal Hitlerian touchiness is downright laughable.
Germany intended to rule the world. What better way than to rule a land that was as expansive, and had the people and resources Russia had?